1. Technical Field
The following description relates to an organic light emitting display apparatus and a method of manufacturing the same.
2. Discussion of the Related Art
As a type of flat panel display apparatus, liquid crystal display (LCD) apparatuses are being the most widely used at present. However, the LCD apparatuses are non-emissive devices that cannot self-emit light, and thus have problems in terms of brightness, a contrast ratio, and a viewing angle range.
As flat panel display apparatuses for overcoming the problems of the LCD apparatuses, organic light emitting display apparatuses are attracting much attention. The organic light emitting display apparatuses are emissive devices that self-emit light, and thus have relatively better brightness, contrast ratio, and viewing angle range than those of the non-emissive devices. Also, because the organic light emitting display apparatuses do not need a separate backlight, the organic light emitting display apparatuses are implemented to have a lighter weight, a thinner thickness, and lower power consumption compared to the LCD apparatuses.
An organic light emitting display apparatus fundamentally includes a thin film transistor (TFT), a first electrode electrically connected to the TFT, a light-emissive organic layer on the first electrode, and a second electrode on the light-emissive organic layer. Because the light-emissive organic layer is vulnerable to water and oxygen, a structure (hereinafter referred to as an “encapsulation structure”) for protecting the light-emissive organic layer from external water or oxygen is needed for preventing a light-emissive defect which is caused by water or oxygen penetrating into the light-emissive organic layer.
FIGS. 1 to 3 are a cross-sectional views of related art organic light emitting display apparatuses having different encapsulation structures (hereinafter referred to as first to third-type encapsulation structures).
As illustrated in FIGS. 1 to 3, the organic light emitting display apparatuses have the same configuration in that the organic light emitting display apparatuses include a TFT substrate 10 including a plurality of TFTs (not shown) and an organic light-emissive device 20 on the TFT substrate 10. A plurality of the organic light-emissive devices 20 have the same configuration in that each of the organic light-emissive devices 20 includes: a first electrode 21 that is formed on the TFT substrate 10 to be electrically connected to the TFT; a bank layer 22 that is formed on the TFT substrate 10 with the first electrode 21 formed thereon, and includes a bank hole which exposes at least one portion of the first electrode 21 corresponding to a light-emissive area; a light-emissive organic layer 23 that is formed on a portion of the first electrode 21 exposed through the bank hole of the bank layer 22; and a second electrode 24 that is formed on the light-emissive organic layer 23.
However, as illustrated in FIG. 1, the first-type encapsulation structure includes: an encapsulation glass 31 that is separated from the organic light-emissive device 20 by a certain distance; and a frit layer 32 that is disposed between the TFT substrate 10 and the encapsulation glass 31 and at an edge of the organic light emitting display apparatus.
According to the first-type encapsulation structure, the encapsulation glass 31 mainly prevents oxygen/water from penetrating into the light-emissive organic layer 23 through a face of the organic light emitting display apparatus, and the frit layer 32 mainly prevents oxygen/water from penetrating into the light-emissive organic layer 23 through a side of the organic light emitting display apparatus. However, the organic light emitting display apparatus having the first-type encapsulation structure is vulnerable to an external impact, and it is impossible to implement the organic light emitting display apparatus as a flexible display apparatus.
To overcome the drawbacks of the first-type encapsulation structure, the second-type and third-type encapsulation substructures have been proposed.
According to the second-type encapsulation structure, as illustrated in FIG. 2, a protective layer 40 is formed on the TFT substrate 10 with the organic light-emissive device 20 formed thereon to entirely cover the organic light-emissive device 20, and an encapsulation plate 60 is adhered onto the TFT substrate 10 with the protective layer 40 formed thereon through an adhesive layer 50. The protective layer 40 includes: a first inorganic layer 41 that entirely covers the organic light-emissive device 20; an organic layer 42 on the first inorganic layer 41; and a second inorganic layer 43 on the organic layer 42.
According to the second-type encapsulation structure, the encapsulation plate 60 and the protective layer 40 mainly prevent oxygen/water from penetrating into the light-emissive organic layer 23 through a face of the organic light emitting display apparatus, and the protective layer 40 (in particular, the first inorganic layer 41) mainly prevents oxygen/water from penetrating into the light-emissive organic layer 23 through a side of the organic light emitting display apparatus.
According to the third-type encapsulation structure, as illustrated in FIG. 3, a plurality of inorganic thin films 71 to 76 and a plurality of organic thin films 81 to 85 are alternately formed on the TFT substrate 10 with the organic light-emissive device 20 to entirely cover the organic light-emissive device 20. According to the third-type encapsulation structure, the inorganic thin films 71 to 76 and the organic thin films 81 to 85 mainly prevent oxygen/water from penetrating into the light-emissive organic layer 23 through a face of the organic light emitting display apparatus. On the other hand, the inorganic thin film 71 mainly prevents oxygen/water from penetrating into the light-emissive organic layer 23 through a side of the organic light emitting display apparatus.
The above-described second-type encapsulation structure enables a thickness of the organic light emitting display apparatus to be greatly reduced, and enables a flexible display apparatus to be realized. However, because the encapsulation plate 60 cannot substantially contribute to preventing oxygen/water from penetrating in a direction parallel to the TFT substrate 10, the light-emissive organic layer 23 is exposed to oxygen/water, and for this reason, there is a relatively high possibility that a quality of the organic light emitting display apparatus is degraded. Also, it is required to use chemical vapor deposition (CVD)/atomic layer deposition (ALD) equipment and coating equipment for forming the first and second inorganic layers 41 and 43 and the organic layer 42, causing an increase in manufacturing cost.
The above-described third-type encapsulation structure uses a flexibility of the organic thin film and a cutoff of water by the inorganic thin film. In order to realize all merits of the organic thin films and the inorganic thin films, the organic thin films and the inorganic thin films are alternately formed. This makes the manufacturing process complicated, extends manufacturing time, and more severely increases cost. Also, because oxygen and water can easily penetrate along an interface of each of the thin films (similarly to the second-type encapsulation structure) the third-type encapsulation structure is also vulnerable to penetration of oxygen/water in the direction parallel to the TFT substrate 10.